QQmlInfo: print ancestor of object if it has no QML engine

This results in the following message for objects without a QML engine:

QML AttachedObject (parent or ancestor of Attached): Binding loop
detected for property "a"

for this QML file, named AttachedObject.qml:

import QtQuick 2.0
import org.qtproject.Test 1.0

Item {
    Attached.a: Attached.a
}

This, in turn, allows the warning to be emitted via the
QQmlEngine::warnings signal, since QQmlEnginePrivate::warning() is now
passed a valid engine. This solves the awkward situation where a
binding loop warning can not be detected at all by auto tests involving
attached C++ objects (as message handlers do not receive these messages
either).

Pick-to: 5.15
Change-Id: I07589974207bd5448d22a6086a52b9230d23e298
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 11 insertions, 0 deletions

diff --git a/tests/auto/qml/qqmlinfo/data/AttachedObject.qml b/tests/auto/qml/qqmlinfo/data/AttachedObject.qml
new file mode 100644
index 0000000000..b714a10a1c
--- /dev/null
+++ b/tests/auto/qml/qqmlinfo/data/AttachedObject.qml
@@ -0,0 +1,11 @@
+import QtQuick 2.0
+import org.qtproject.Test 1.0
+
+Item {
+    Attached.a: Attached.a
+
+    Rectangle {
+        width: height + 1
+        height: width + 1
+    }
+}